1. Technical Field
This disclosure relates to a head capping member, a head maintenance or recovery device, a device for ejecting a liquid drop, and an image forming apparatus.
2. Description of the Related Art
As an image forming apparatus such as a printer, a facsimile, a copying machine, and a composite machine thereof, for example, an ink jet recording apparatus is known. Such an ink jet recording apparatus conducts recording (for example, image formation, image printing, character printing, and printing may be used as synonyms.) by ejecting an ink drop as a drop of liquid (recording liquid) onto a medium to be recorded such as a recording paper (hereinafter, it may be referred to as a “paper sheet”, the material of which is not limited to paper, and it may be also referred to as a recording medium, a transfer paper, a transfer material and a material to be recorded) from a recording head composed of a liquid ejecting head(s).
Thus, in a device for ejecting a liquid drop from a liquid ejecting head, a maintenance or recovery mechanism (device) for maintaining or recovering the reliability of the head is essential for preventing loss of normal ejection thereof, since a foreign matter such as thickened or dried ink, dust and contaminants adheres to the outer face of nozzle of the head so as to cause the clogging of the nozzle or an air-damper phenomenon is caused by, for example, the generation of air bubbles, at the inside of the nozzle.
The maintenance or recovery mechanism has a cap (capping member) for sealing the nozzle face (liquid drop ejecting face) of the head. Also, for example, an operation (head suction or nozzle suction) of sucking ink provided from the nozzle and filled in the head using suction means such as a suction pump communicating with the inside of the cap, an operation of wiping the head surface with a wiper blade for which an elastic material such as rubber is used, and a blank ejection operation (also refereed to as a preliminary ejection operation) of ejecting thickened ink or mixed color ink located on the inside of the nozzle and around the outlet thereof by ejecting ink such that no influence is provided to image formation, are appropriately combined, so as to conduct an operation of removing, for example, bubbles in a liquid chamber, thickened ink and adhering contaminants, thereby keeping the condition which can conduct stable liquid drop ejection.
One of conventional capping means, as disclosed in Japanese Patent Application Publication No. 2002-240325, includes a capping member on which a recess and a suction port are formed, and a capillary force generation member which is formed separately from the capping member, forms gap with a wall constituting the recess and is arranged so as to generate capillary force against a face of the recess on which face a suction port communicating with suction means is formed, and, thereby, reduces the amount of remaining ink in the capping member.
Also, another one, as disclosed in Japanese Patent Application Publication No. 2005-271458, provides at least two inclined planes inclining toward an outlet on the bottom portion of a capping member, wherein the sum of the angle of the inclined plane with respect to the horizontal plane and the contact angle of a recording liquid drop with respect to a member forming the inclined plane is equal to or greater than 70°, whereby the amount of remaining highly viscous recording liquid in the capping member can be reduced.
As also disclosed in Japanese Patent Application Publication No. 2005-271458 described above, characteristics required for recording liquid (ink) for ink jet recording are color tone, image density, bleeding, etc., for attaining a high image quality, dissolution or dispersion stability, storage stability, ejection stability, etc., of a coloring agent in ink, for attaining the reliability, water resistance, light fastness, etc., for retaining the keeping quality of a recorded image, the quick-drying property of ink, etc., for attaining the speeding-up, and, conventionally, various attempts to satisfy these requirements have been made. For example, as a coloring agent for ink, dye inks were initially trend in view of the good coloring property or high reliability thereof, but, recently, ink compositions for which a pigment such as carbon blacks tends to be used in order to provide a recorded image with a certain light fastness or water resistance.
Then, approaches for suppressing the viscosity rise of a conventional recording liquid as much as possible have been examined in order to improve the reliability of an image forming apparatus, but it is necessary to use a highly viscous recording liquid in order that a high quality image can be formed on a normal paper sheet.
Herein, when, for example, a recording liquid is used which is prepared to contain, at least, a coloring agent and wetting agent dispersible in water and to rapidly thicken (the rate of viscosity rise (mPa·s/%) being over 50) in a water evaporation rate of 30-45% to the initial weight, a significant improvement may be found against nozzle failure (defective ejection) caused by the clogging of nozzle with, for example, a dye precipitate or the solid content of a dispersion-instable pigment, a new problem which is considered not to occur in the conventional recording liquid has been found, due to the evaporation rate—viscosity characteristic.
That is, a phenomenon has been found such that recording liquid adhering to and remaining on the inside of a suction cap, for example, as a result of a maintenance or recovery operation such as cleaning, eliminates water from the nozzle of the head and, thereby, defective ejection is caused.
As described more specifically, the maintenance or recovery mechanism includes a suction cap for capping the nozzle face of a recording head and sucking and ejecting recording liquid from the nozzle, but when printing is continued for a long time, the recording liquid ejected to and remaining on the inside of the suction cap due to the maintenance or recovery mechanism dries according to the environment of the placed apparatus. Then, when the recording head is capped with the suction cap in such a condition, the recording liquid in a dry condition eliminates water content from the recording liquid in the nozzle, that is, the water content of the recording liquid in the nozzle of the recording liquid is eliminated, thereby causing rapid viscosity rise thereof. As a result, the recording liquid in the nozzle is thickened so as to cause the clogging thereof and the defective ejection.
From such a viewpoint, it is necessary to surely prevent the recording liquid from remaining in the cap, but there is a problem such that a capping member utilizing capillary action as disclosed in Japanese Patent Application Publication No. 2002-240325 could provide no solution when the recording liquid with a high viscosity and a high rate of viscosity rise as described above is used, and there is also a problem such that a capping member as disclosed in Japanese Patent Application Publication No. 2005-271458 could not necessarily prevent the recording liquid from remaining.